Underwater operation of a DBD plasma jet

A plasma jet produced in water using a submerged ac excited electrode in a coaxial dielectric barrier discharge configuration was studied. Plasma jet formation was found to occur only while the source was submerged. Plasma jet operation was characterized with and without gas flow. It was found that over 60% of the discharge power was deposited into the water and did not vary appreciably with excitation frequency. Presumably the remaining power fraction went into excitation, ionization and local electrode heating. Emission spectra of the jet revealed nitrogen, hydrogen, hydroxyl and oxygen emission lines. Operation of the plasma jet in water containing the oxidation–reduction indicator methylene blue dye resulted in a marked clearing of the water as observed visually and with a spectrophotometer, suggesting plasma-induced chemical reactivity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85414/1/psst10_2_025001.pd

Characterization of the evolution of underwater DBD plasma jet

An air plasma jet formed underwater using a coaxial DBD electrode configuration with gas flow is being studied for water treatment applications. The arc-like behavior of the discharge in the absence of any obvious return electrode is not well understood. This study seeks to understand the underlying nature of the arc-like jet mode by studying the evolution of the discharge from microdischarge to jet mode. Photographic and spectroscopic data are used to develop a phenomenological model of discharge evolution. Time-averaged spectra were used to assign an average plume and electron temperature. Calculated jet temperatures were consistent with observed affects such as melting and oxide layer formation on a downstream substrate. The capacity of the microdischarge mode to decompose organic dye in water as a function of time, confirmed previously in the jet mode, was also demonstrated in the absence of the jet.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90806/1/0963-0252_20_3_034018.pd

Reframing outcome measures for thrombolytics in acute ischemic stroke

An informed consent conversation examining relevant research and discussing the potential benefits and harms of thrombolytic therapy in acute stroke

Efficacy of REACH Forgiveness across Cultures

Across cultures, most people agree that forgiveness is a virtue. However, culture may influence how willing one should be to forgive and how one might express forgiveness. At a university in the United States, we recruited both foreign-extraction students and domestic students (N = 102) to participate in a six-hour REACH Forgiveness intervention. We investigated the efficacy of the intervention overall as well as whether foreign-extraction and domestic students responded differently to treatment. Forgiveness was assessed using two measures—decisional forgiveness and emotional forgiveness. The six-hour REACH Forgiveness intervention improved participants’ ratings of emotional forgiveness, but not decisional forgiveness, regardless of their culture. Thus, the REACH Forgiveness intervention appears equally efficacious for participants from different cultural backgrounds when conducted in the United States with college students

Effects of Postural Load Perturbations on the Stroke-impaired Spinal Circuitry

Objective Transitioning from supported sitting position to standing activities requires coordinated interactions among postural muscles with appropriate reflexive responses to adapt to an increase in postural loading. Previous studies have found the failure to accommodate the challenge of increased postural loads in the stroke-impaired nervous system. In this study, we examined the H-reflex in response to different magnitudes of loads under static postural conditions, and compared the responses directly between individuals with a stroke-impaired nervous system and those with a non-neurologically impaired nervous system. We tested the hypothesis that the reflex amplitude would increase with increased load during standing in the non-neurologically impaired nervous system but would remain unchanged in the stroke-impaired nervous system. Methods Nine individuals with a history of stroke and thirteen healthy individuals each completed a reflex recording during static standing, under 3 loading conditions (1) -20% of body weight unloaded condition, (2) body weight condition, (3) +20% of body weight loaded condition. H-reflexes were elicited via electrical stimulation at the tibial nerve, and reflex responses were recorded on the soleus muscle. Results We observed increased H-reflex amplitudes under the weighted condition in controlled participants, compared to body weight and unweighted conditions. We observed a higher Hmax/Mmax ratio in the paretic leg regardless of loading conditions, which is in agreement with previous literature reporting higher H-reflex amplitudes in individuals with lesions in the central iv nervous system. In both paretic and non-paretic legs, we did not observe changes in H-reflex amplitudes with each loading condition. Conclusion Our findings suggest that an impaired ability to modulate the H-reflex pathway appropriately to increase the reflex stiffness of Ia afferent pathway, in response to changes in postural loads, may explain the reduced ability to adequately bear weight through lower limbs for standing, locomotion, and postural support tasks in individuals post-stroke. Significance The results of this study support the importance of early facilitation of weight-bearing activities with the incorporation of postural loading and unloading training, when considering clinical application for stroke recovery. Future studies will examine the adaptations of the Ia afferent pathway relative to postural loading during the subacute phases post-stroke, and its role during loaded and unloaded overground walking

Effects of Crumb Rubber on the Shear Strength of Sand: An Experimental Study

The application of waste rubber tires for ground improvement helps to improve the environment by recycling and reusing it as admixtures. This research aims to investigate the shear strength parameters of rubber-sand mixtures. By using crumb rubber with a constant size (425μm), the sand is replaced by different percentages (0, 2.5, 5.0, 7.5, and 10%) of crumb rubber by weight. A direct shear box test is used to determine the shear strength parameters of rubber-sand mixtures with two different controlled densities. The samples were loaded with normal stresses of 20, 40 and 80kPa and were sheared at a rate of 1mm/min. Although, this experiment discovered that crumb rubbers improve the shear strength parameters in loose sand, however, a reduction in shear strength parameters was found in dense sand. Moreover, it was observed that the inclusion of crumb rubbers into sand greatly improve the strain energy of both loose and dense sand. Likewise, rubber has a low unit weight which makes it suitable for lightweight backfill materials. The surface properties of rubber should be further studied to understand the contribution of shear strength in the rubber-sand mixture

Engineering tyrosine-based electron flow pathways in proteins: The case of aplysia myoglobin

Tyrosine residues can act as redox cofactors that provide an electron transfer ("hole-hopping") route that enhances the rate of ferryl heme iron reduction by externally added reductants, for example, ascorbate. Aplysia fasciata myoglobin, having no naturally occurring tyrosines but 15 phenylalanines that can be selectively mutated to tyrosine residues, provides an ideal protein with which to study such through-protein electron transfer pathways and ways to manipulate them. Two surface exposed phenylalanines that are close to the heme have been mutated to tyrosines (F42Y, F98Y). In both of these, the rate of ferryl heme reduction increased by up to 3 orders of magnitude. This result cannot be explained in terms of distance or redox potential change between donor and acceptor but indicates that tyrosines, by virtue of their ability to form radicals, act as redox cofactors in a new pathway. The mechanism is discussed in terms of the Marcus theory and the specific protonation/deprotonation states of the oxoferryl iron and tyrosine. Tyrosine radicals have been observed and quantified by EPR spectroscopy in both mutants, consistent with the proposed mechanism. The location of each radical is unambiguous and allows us to validate theoretical methods that assign radical location on the basis of EPR hyperfine structure. Mutation to tyrosine decreases the lipid peroxidase activity of this myoglobin in the presence of low concentrations of reductant, and the possibility of decreasing the intrinsic toxicity of hemoglobin by introduction of these pathways is discussed. © 2012 American Chemical Society

Large-scale detector testing for the GAPS Si(Li) Tracker

Lithium-drifted silicon [Si(Li)] has been used for decades as an ionizing radiation detector in nuclear, particle, and astrophysical experiments, though such detectors have frequently been limited to small sizes (few cm$^2$) and cryogenic operating temperatures. The 10-cm-diameter Si(Li) detectors developed for the General Antiparticle Spectrometer (GAPS) balloon-borne dark matter experiment are novel particularly for their requirements of low cost, large sensitive area (~10 m$^2$ for the full 1440-detector array), high temperatures (near -40\,^\circC), and energy resolution below 4 keV FWHM for 20--100-keV x-rays. Previous works have discussed the manufacturing, passivation, and small-scale testing of prototype GAPS Si(Li) detectors. Here we show for the first time the results from detailed characterization of over 1100 flight detectors, illustrating the consistent intrinsic low-noise performance of a large sample of GAPS detectors. This work demonstrates the feasibility of large-area and low-cost Si(Li) detector arrays for next-generation astrophysics and nuclear physics applications.Comment: Updated to version accepted in IEEE Trans Nucl Sci. Minor changes to text, fixed plotting error on Fig. 5. Conclusions unchange